Identifying Genetic Disorders in Equine Embryos

According to Hinrichs, the team has achieved success rates greater than 97% in identifying genetic disorders. She noted that the test is currently being offered with the provision that there is still a small chance (<3%) for error.

Photo: E.L. Squires, MS, PhD

What if you could test your future foal to see if it had a genetic disorder or find out what sex it would be within days of breeding your mare? Texas A&M University researchers have announced the availability of a test that can determine fetal sex or the presence of a genetic disorder within days of conception.

"This clinical method for testing embryos almost immediately after breeding, a process called preimplantation genetic diagnosis, or PGD, will help eliminate the occurrence of some devastating genetic diseases," explained lead researcher Katrin Hinrichs, DVM, PhD, a professor in the Department of Veterinary Physiology and Pharmacology. "These include diseases found in American Quarter Horses, such as hereditary equine regional dermal asthenia (HERDA), glycogen branching enzyme deficiency, and hyperkalemic periodic paralysis (HYPP), as well as severe combined immunodeficiency disorder and cerebellar abiotrophy, which have plagued Arabians."

With this test the veterinarian "flushes" the fertilized embryo from the mare approximately seven days post-breeding (prior to the embryo implanting in the uterine wall, as the name suggests). After removing a few cells from the area of the embryo that becomes the placenta and testing them for genetic disorders, the practitioner transfers the embryo into a recipient mare.

"Our studies show that the embryos are viable after biopsy and provide normal pregnancy rates after transfer and that 100% (9/9) of mares that received transfers of biopsied embryos had uneventful pregnancies that resulted in the birth of healthy foals," Hinrichs said.

The team also found a way to amplify embryos' DNA to determine fetal sex.

"Together, the ... embryo biopsy with the whole genome amplification using a commercially-available kit ... are accurate enough that this technique can be used in a clinical setting," added Hinrichs. "Currently, we are testing embryos positive for common genetic diseases to establish the accuracy of the procedure for these specific genes."

According to Hinrichs, the team has achieved success rates greater than 97% in identifying genetic disorders. She noted that the test is currently being offered with the provision that there is still a small chance (<3%) for error.

The study, "Accuracy or preimplantation genetic diagnosis using cells biopsied from equine blastocysts," was published in the December 2011 edition of Reproduction, Fertility, and Development. The abstract is available on PubMed.

About the Author

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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